Representing Signals

Numeric Arrays

The central data construct in the MATLAB® environment is
the numeric array, an ordered collection of real
or complex numeric data with two or more dimensions. The basic data
objects of signal processing (one-dimensional signals or sequences,
multichannel signals, and two-dimensional signals) are all naturally
suited to array representation.

Vector Representation

MATLAB represents ordinary one-dimensional sampled
data signals, or sequences, as vectors.
Vectors are 1-by-n or n-by-1
arrays, where n is the number of samples in the
sequence. One way to introduce a sequence is to enter it as a list
of elements at the command prompt. The statement

x = [4 3 7 -9 1];

creates a simple five-element real sequence in a row vector.
Transposition turns the sequence into a column vector

x = x';

x =
4
3
7
-9
1

Column orientation is preferable for single channel signals
because it extends naturally to the multichannel case. For multichannel
data, each column of a matrix represents one channel. Each row of
such a matrix then corresponds to a sample point. A three-channel
signal that consists of x, 2x,
and x/π is

If the sequence has complex-valued elements, the transpose operator
takes the conjugate of the sequence elements. To transform a complex-valued
row vector into a column vector without taking conjugates, use the .' or
non-conjugate transpose:

x = [1-i 3+i 2+3*i 4-2*i]; % 1-by-4 vector
x = x.'; % 4-by-1 vector

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